The invention relates to an electrical switch having upper and lower housing components which can be connected to one another in a locking fashion. Contact lugs being in a normally off position are arranged in receptacles of the lower housing component. A contact element with a switching contact is arranged in the upper housing component. The contact element is movable via a pressure spring and a slider rod. The slider rod projects out of the upper housing component and is coupled to an actuation element. The contact element is caused to flip between an off (open) position, in which the switching contact does not touch the resting contact, and an on (closed) position, in which the switching contact touches the contacts.
Such electrical switches are used for switching on and off electrical DC or AC circuits in which high currents, for example, of up to 20 A can flow. They are used, in particular, in machine tools with a high power consumption, for example in right angle grinders or circular saws.
German Offenlegungsschrift DE-OS 31 26 816 discloses an electrical switch in which a carriage can be linearly displaced by means of an actuation element via a slider rod and a bow-shaped catch spring, a contact bridge for bypassing the fixed contacts arranged in the housing of the electrical switch being attached to the carriage. When the switch is switched off, in particular at high currents, an arc occurs between the contact bridge and the fixed contacts which causes the contacts to be eroded. If copper is used as material for the contacts, even after a short period of use the impedance of the switch becomes high due to the badly conducting copper oxide produced as a result of the erosion of the contacts so that severe, often unacceptably high heating at the switch occurs. Particularly in DC operation in which, in contrast with AC operation, no zero cross-over phase occurs which extinguishes the arc, the erosion of the contacts can be so strong that after a few switching operations and thus after a short period of use the switch becomes unusable.
In order to eliminate these disadvantages, it is known to coat the copper contacts with silver. The silver layer conducts the electrical current with the onset of erosion of the contacts much better than a copper layer. However, this too does not completely prevent the shortening of the theoretically possible service life of the switch. The much higher price for such a silver coating is also disadvantageous.
In addition, switches have also been disclosed in which contact lugs consisting of copper and having a normally opened contact are arranged in the housing, a rotatable contact rocker which is moved by an actuation element via a slider rod and a pressure spring and has a switching contact bypassing the normally opened contacts. Here too, the aforesaid disadvantage occurs, namely very severe erosion at the normally opened contact, which makes the switch unusable even after a short period of use.